Snakes are vertebrates, not invertebrates. A vertebrate is an animal that possesses a backbone or spinal column. Thus snakes and other reptiles are all vertebrates, as are mammals, birds, amphibians and fish.
As an example, the Eastern kingsnake's kingdom is Animalia, living things that move around and survive by consuming other living things. Its phylum is chordata, which are animals with nerve cords, and its class is reptilia, cold-blooded air-breathing vertebrates with lungs (rather than gills). The kingsnake is of the order squamata, the scaled reptiles. All the preceding applies to all snakes. Eastern kingsnakes are of the family colubridae: nonvenomous, mostly bare-faced, having no vestigial limbs. Finally, Eastern kingsnakes are genus lampropeltis (shining, beautiful scales) and species getula (connected to the people of Morocco).